ZyXEL Communications MSC1000G Series, Руководство пользователя

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Chapter 9 Subscriber Port Setup Screens
Management Switch Card User’s Guide
208
ISDN in Europe uses a frequency range of up to 80 kHz, while ISDN in Japan uses a frequency
range of up to 640 kHz. ADSL utilizes the 1.1 MHz band. Both ADSL2 and ADSL 2+ utilize the 2.2
MHz band.
An example is shown next. VDSL Line 1 and ADSL Line 2 are in the same binder. Crosstalk occurs
when the ADSL signal flows from CO (B) and is near to CO (A) ’s ONU (Optical Network Unit)
location. Besides, higher Line 1 PSD causes higher interference to the Line 2 . CPE (B) receives
signal with higher attenuation. With DPBO enabled on the CO (A) , it decreases the PSD level and
reduces the crosstalk impact on other service lines.
Figure 127
DPBO Resolves Downstream Far-End Crosstalk
9.2.9 UPBO/DPBO Electrical Length
The distance between a cabinet and the central office is an important parameter of DPBO settings
as mentioned in
Section 9.2.8 on page 207 . The electrical length is used instead of the real physical
distance according to G.997.1 format. Depending on the cable type, the line used and physical line
length, you can calculate the electrical length (in dB). For example, if the distance is 1 kilometer
and you use 24 AWG cable type, the electrical length 20.5 dB is recommended.
The following table displays the calculation from a real length to an electrical length.
9.2.10 Rate Adaption
Rate adaption is the ability of a device to adjust from the configured transmission rate to the
attainable transmission rate automatically depending on the line quality. The VDSL transmission
rate then stays at the new rate or adjusts if line quality improves or deteriorates.
The switch determines line quality using the Signal-to-Noise Ratio (SNR). SNR is the ratio of signal
power to noise power. A low SNR indicates poor line quality.
VDSL
CPE (B)
Line1 (150m)
Line2 (600m)
No-DPBO
DPBO
ADSL
CO (A)
ADSL
CPE (A)
VDSL
CO (B)
Table 90
Real Length to Electrical Length
CABLE TYPE REAL LENGTH TO ELECTRICAL LENGTH A B C
22 AWG =16.2*(cable length in kilometer) 0 0 0
24 AWG =20.5*(cable length in kilometer) 0 1 0
26 AWG =25.8*(cable length in kilometer) 0 1.0039065 -0.0039065